> For the complete documentation index, see [llms.txt](https://sec88.0x88.online/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sec88.0x88.online/android-appsec/smali/patching-with-smali.md). # Smali Code Patching Guide ### Changing the Return Value in Methods #### Example: `checkDebugger()` Function The original `checkDebugger()` function in smali checks whether a debugger is connected. By modifying this function, we can change its behavior to always return a specific result. #### Original Code ```smali .method public checkDebugger()Z .locals 1 .line 30 invoke-static {}, Landroid/os/Debug;->isDebuggerConnected()Z move-result v0 return v0 .end method ``` In this case, the method returns the actual result of `isDebuggerConnected()`. To modify it, we can overwrite the value of `v0` before returning it. #### Modified Code ```smali .method public checkDebugger()Z .locals 1 .line 30 invoke-static {}, Landroid/os/Debug;->isDebuggerConnected()Z move-result v0 const v0, 0x0 # Overwrite the result to always be false return v0 .end method ``` Now, the method always returns `false` (represented by `0x0`), no matter the actual result of the `isDebuggerConnected()` function. *** ### Flipping the Logic in Conditionals (IF-ELSE-GOTO Patching) #### Example: Processing `getHit()` Method in a Game Here, we modify a method that processes a player getting hit, depending on whether the player has a shield. By flipping the conditional logic, we can change how the game behaves. #### Original Code ```smali .method public getHit()V .locals 3 .line 37 iget-boolean v0, p0, Lcom/apphacking/smalitwo/Player;->shield:Z const/4 v1, 0x0 const/4 v2, 0x1 if-ne v0, v2, :cond_0 # If shield is not active, go to cond_0 .line 39 iput-boolean v1, p0, Lcom/apphacking/smalitwo/Player;->shield:Z goto :goto_0 .line 42 :cond_0 iget v0, p0, Lcom/apphacking/smalitwo/Player;->lives:I sub-int/2addr v0, v2 iput v0, p0, Lcom/apphacking/smalitwo/Player;->lives:I .line 44 if-lez v0, :cond_1 .line 46 iput-boolean v2, p0, Lcom/apphacking/smalitwo/Player;->state:Z goto :goto_0 .line 49 :cond_1 iput-boolean v1, p0, Lcom/apphacking/smalitwo/Player;->state:Z .line 52 :goto_0 return-void .end method ``` In this code, when the player has a shield (`if-ne v0, v2`), they don't lose lives. To flip this logic, we can change the `if-ne` to `if-eq` so that now the player will lose lives when they have a shield. #### Modified Code ```smali .method public getHit()V .locals 3 .line 37 iget-boolean v0, p0, Lcom/apphacking/smalitwo/Player;->shield:Z const/4 v1, 0x0 const/4 v2, 0x1 if-eq v0, v2, :cond_0 # If shield is active, go to cond_0 (Flipped Logic) .line 39 iput-boolean v1, p0, Lcom/apphacking/smalitwo/Player;->shield:Z goto :goto_0 .line 42 :cond_0 iget v0, p0, Lcom/apphacking/smalitwo/Player;->lives:I sub-int/2addr v0, v2 iput v0, p0, Lcom/apphacking/smalitwo/Player;->lives:I .line 44 if-lez v0, :cond_1 .line 46 iput-boolean v2, p0, Lcom/apphacking/smalitwo/Player;->state:Z goto :goto_0 .line 49 :cond_1 iput-boolean v1, p0, Lcom/apphacking/smalitwo/Player;->state:Z .line 52 :goto_0 return-void .end method ``` Now, the game logic is reversed, and the player loses lives when they have a shield. *** ### Deleting Code to Alter Game Logic In some cases, you can remove certain instructions to alter the game behavior entirely. #### Example: `processGame()` Method in Java ```java public void processGame() { // Create new Player Object Player player = new Player(); if (player.hasItem(MasterCap)) { player.power += 100; } else { player.power += 10; } } ``` In smali, this code translates into conditional logic that adds power based on whether the player has the `MasterCap`. #### Original Smali Code ```smali .method public hasItem(Lcom/apphacking/smalitwo/Player;)V .locals 1 .param p1, "player" # Lcom/apphacking/smalitwo/Player; .line 15 iget-boolean v0, p1, Lcom/apphacking/smalitwo/Player;->masterCap:Z if-eqz v0, :cond_0 # Check if the player does not have the MasterCap .line 17 iget v0, p1, Lcom/apphacking/smalitwo/Player;->power:I add-int/lit8 v0, v0, 0x64 # Add 100 power iput v0, p1, Lcom/apphacking/smalitwo/Player;->power:I goto :goto_0 .line 20 :cond_0 iget v0, p1, Lcom/apphacking/smalitwo/Player;->power:I add-int/lit8 v0, v0, 0xA # Add 10 power iput v0, p1, Lcom/apphacking/smalitwo/Player;->power:I .line 23 :goto_0 return-void .end method ``` By removing the `if-eqz` line, the game will always give the player 100 power, regardless of whether they have the `MasterCap`. #### Modified Code ```smali .method public hasItem(Lcom/apphacking/smalitwo/Player;)V .locals 1 .param p1, "player" # Lcom/apphacking/smalitwo/Player; .line 17 iget v0, p1, Lcom/apphacking/smalitwo/Player;->power:I add-int/lit8 v0, v0, 0x64 # Always add 100 power iput v0, p1, Lcom/apphacking/smalitwo/Player;->power:I .line 23 return-void .end method ``` By eliminating the condition, the player now gets a 100 power boost unconditionally. *** ### Changing Jump Instructions Jump instructions (`goto`, `if-*`) can be modified to change how the program flow behaves. #### Example: Modifying GOTO In the same method, we can alter the jump instruction to make the player gain 110 power instead of choosing between 100 or 10. #### Original Code ```smali goto :goto_0 ``` #### Modified Code ```smali goto :cond_0 # Redirect to give both 10 and 100 power ``` Now the program first adds 10 power and then immediately adds 100 power, giving a total of 110. *** ### Additional Method: Manipulating Currency in a Game #### New Method: `increaseCurrency()` This method will increase the player's in-game currency. ```smali .method public increaseCurrency()V .locals 2 .line 25 iget v0, p0, Lcom/apphacking/smalitwo/Player;->currency:I const/16 v1, 0x3E8 # Add 1000 currency add-int/2addr v0, v1 iput v0, p0, Lcom/apphacking/smalitwo/Player;->currency:I .line 28 return-void .end method ``` Now the player will receive 1000 in-game currency every time this method is called. --- # Agent Instructions This documentation is published with GitBook. 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